Razor blade
A razor blade is provided, which achieves improved safety in use and reduced cutting resistance to an object to be cut such as beard and hair, as compared with conventional razor blades. This razor blade can be obtained by using, as a silicon thin sheet, a single crystal silicon material such as Si wafer or a polycrystalline silicon material including relatively large silicon crystal grains, forming at least one opening in the silicon thin sheet by chemical etching, and forming a cutting edge made of silicon single crystal by ion beam etching without machining such that the cutting edge projects into the opening and has a nose radius of 0.5 μm or less, and preferably 0.1 μm or less.
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The present invention relates to a razor blade, which is excellent in safety and cutting performance for an object to be cut such as beard and hair, and particularly the razor blade having a cutting edge, which is made of a silicon single crystal and has an extremely small nose radius.
BACKGROUND ARTConventional razor blades with a cutting edge linearly formed along a side of a thin steel sheet may accidentally cause injury to skin in use. Therefore, it is a major task to improve the safety. For example, it has been proposed to reduce the damage to the skin by winding a plurality of thin wires around the razor blade at regular intervals. However, from the viewpoint of improving the safety, while maintaining excellent cutting performance for an object to be cut such as beard and hair, a satisfactory level has not been always achieved.
In addition, various kinds of net blades have been proposed to achieve a further improvement in safety. For example, such net blades are disclosed in U.S. Pat. No. 4,875,288 and European Patent No. 0 541 723 B1. In the case of a net blade made of a metal material, however, since its cutting edge is formed by machining, there is a limitation with respect to the formation of the cutting edge with a small nose radius. For example, even when burrs generated at the cutting edge by grinding are removed by precise polishing such as lapping, it is difficult to obtain a nose radius of 1 μm or less. Due to this reason, it has not been achieved yet to smoothly shave beard or hair by the net blade made of a stainless steel except for a razor blade with a linear cutting edge of a nose radius of approximately 0.1 μm, which is obtained by grinding a stainless steel sheet. Moreover, in the conventional razor blades on the market, a technique of forming the cutting edge of a nose radius of 0.1 μm or less has not been sufficiently established yet.
SUMMARY OF THE INVENTIONTherefore, a primary concern of the present invention is to provide a razor blade with a cutting edge of a nose radius (R) of 0.5 μm or less, which has the capability of providing remarkably improved safety in use, and a reduction in cutting resistance to an object to be cut such as beard and hair, as compared with conventional razor blades.
That is, the razor blade of the present invention is made of a silicon thin sheet having at least one opening and a cutting edge projecting into the opening, and wherein the cutting edge is made of silicon single crystal, and a nose radius of the cutting edge is 0.5 μm or less, and particularly 0.1 μm or less.
In the razor blade described above of the present invention, it is preferred that the silicon thin sheet is a silicon single crystal material such as Si wafer. In this case, as described below, it is possible to efficiently manufacture a net-like razor blade or a razor blade having a plurality of slits by silicon micromachining technique.
In addition, it is preferred that the razor blade according to a preferred embodiment of the present invention is a net blade made of the silicon thin sheet having a plurality of openings and the cutting edge projecting into each of the openings. Alternatively, it is preferred that the razor blade is made of the silicon thin sheet having a plurality of openings and the cutting edge projecting into each of the openings, and each of the openings is configured in a rectangular shape, which is arranged in substantially parallel with an adjacent opening in its longitudinal direction.
These and still other objects and advantages of the present invention will become more apparent from the best mode for carrying out the invention explained in details below, referring to the attached drawings.
A razor blade of the present invention has a cutting edge of silicon single crystal, which is formed by silicon micromachining technique with use of a silicon single crystal material such as Si wafer or a polycrystalline silicon material including relatively large silicon crystal grains, without applying mechanical grinding or polishing. The silicon micromachining technique means a technique of forming an ultra-fine three-dimensional structure by a physical etching such as ion-beam etching, a chemical etching (anisotropic etching), or a combination thereof.
In general, single crystal has a long-range order in atomic arrangement, and also a long-range order in direction dependency of bonding between atoms (covalent bonding between silicon atoms). Therefore, an intersection between planes of atomic arrangements, i.e., the intersection between crystal planes is maintained over the long range. By using this intersection as a cutting edge, it is possible to theoretically form the cutting edge with an extremely small nose radius (R). Such an ultra-fine cutting edge can be achieved by an ultra-microfabrication using the above-described silicon micromachining technique. Moreover, a single-crystal cutting edge of the razor blade can be formed by stacking silicon atoms one by one to form the intersection between the atomic arrangements, which is included in the technical concept of the present invention.
By the way, an interest of the present invention is not to provide a simple razor blade having a plurality of fine openings. That is, as described above, the present invention has been achieved by finding that the cutting edge made of silicon single crystal, which is formed so as to project into each of the openings (blade openings), and have a nose radius of 0.5 μm or less, preferably 0.1 μm or less in consideration of single crystal properties of Si, provides excellent cutting performance as well as the safety in use.
As described, the razor blade of the present invention can be manufactured by using the silicon micromachining technique. Concretely, it is preferred to adopt at least one of chemical etching and ion-beam etching utilized to fabricate silicon in the semiconductor technical field. To satisfy both of the manufacturing efficiency and the required precision to the cutting edge, a preferred manufacturing method is introduced below. That is, at least one opening is formed in a silicon thin sheet by the chemical etching, and then the cutting edge made of silicon single crystal is formed so as to project into the opening and have a nose radius of 0.5 μm or less by the ion-beam etching.
In addition, the razor blade of the present invention has at least one opening, into which the cutting edge projects. In practical use, a plurality of openings can be formed in various kinds of patterns. For example, a net blade 1 shown in
In addition, as shown in
It is also preferred that a cutting edge angle (θ), which is defined between a bottom surface 12 of the razor blade and an inclined surface 13 extending from a top surface 11 to the bottom surface 12 of the razor blade in the opening 20, as shown in
In addition, it is preferred that the cutting edge 10 formed in the longitudinal direction of the opening 20 is composed of cutting-edge forming portions 14 and cutting-edge free portions 15, which are arranged in a staggered manner, as shown in
As shown in
Alternatively, as shown in
It is also preferred that a surface layer 30 formed on the cutting edge 10 of the razor blade of the present invention is provided with a silicon oxide layer, at least one of metal and alloy layers, or an amorphous silicon layer. In particular, as shown in
When the silicon oxide layer is formed as the surface layer 30, it is possible to improve resistance to breakage such as cracks resulting from a local stress orientation totally or partially induced in the razor blade during the shaving process. For example, when the opening 20 is of a substantially square shape, the inclined surfaces intersect to each other by 90° in the opening. The silicon oxide layer can be formed along this intersection line. When the silicon oxide layer is formed on a surface of the razor blade that contacts the skin in use, the cutting resistance between the skin and the razor blade decreases. Thus, the razor blade becomes gentle to skin. The silicon oxide layer can be formed in the outermost surface of the razor blade by means of selective oxidation of silicon.
In addition, the metal layer or the alloy layer may be formed as the surface layer 30. For example, the surface layer can be formed by a physical deposition of one of metals having excellent ductility and corrosion resistance such as Au, Pt, Ni, Ti and Al or an alloy thereof. As in the above-described case, it is possible to improve the resistance to breakage such as cracks resulting from a local stress orientation totally or partially induced in the razor blade during the shaving process. Alternatively, in place of the silicon oxide layer, the amorphous silicon layer may be formed. For example, the amorphous silicon layer can be formed by remelting and quenching with laser-beam irradiation, an irradiation damage method using electron beam, neutron beam or the like, or ion implantation.
In addition, a polycrystalline silicon layer may be formed in a region other than the nose (R) of the cutting edge. The polycrystalline silicon layer can be formed by controlling the parameters in a similar method to the case of forming the amorphous silicon layer. When the polycrystalline silicon layer is formed on the cutting edge, there is a fear that micro-chipping occurs at the grain boundary. However, when the polycrystalline silicon layer is formed in the region other than the nose (R), it is possible to increase the resistance to breakage such as large cracks of the razor blade.
It is also preferred to form microscopic asperities in a surface of the razor blade 1, which contacts the user's skin in use, except for the vicinity of the cutting edge. In this case, due to a reduction in contact area between the razor blade and the skin during the shaving process, it is possible to smoothly get a shave. In addition, as shown in
As shown in
A polycrystalline silicon block having a crystal grain size of approximately 10 mm was cut to obtain a sheet-like silicon single crystal having the thickness of 0.3 mm and the square shape of 7 mm×7 mm. Then, square openings (blade openings) having the size of 1.5 mm×1.5 mm were formed in a pattern shown in
From a SEM observation of the cutting edge 10 of the obtained razor blade 1, it was confirmed that the nose radius (R) of the cutting edge is smaller than 10 nm. The cutting resistance in the case of cutting a single hair was 1 gf. On the other hand, the cutting resistance in the case of cutting the single hair by use of a commercially available razor blade having a cutting edge angle of approximately 20° was 10 gf. Thus, it was confirmed that the razor blade of this example is one-tenth smaller in cutting resistance than the commercially available razor blade. In addition, five of the same razor blades were arranged in parallel, and then mounted on a required body by use of an adhesive. A shaving process was performed, while these razor blades being pressed against the skin. Since the size of the square opening is very small, smooth shaving was achieved without causing any injury of the skin.
EXAMPLE 2A polycrystalline silicon block having a crystal grain size of approximately 10 mm was cut to obtain a sheet-like silicon single crystal having the thickness of 0.3 mm and the square shape of 7 mm×7 mm. Then, rectangular openings (blade openings) having the size of 1.5 mm×5 mm were formed in a pattern shown in
From a SEM observation of the cutting edge 10 of the obtained razor blade, it was confirmed that the nose radius (R) of the cutting edge is smaller than 10 nm. As in the case of Example 1, the razor blade of this Example was compared to the commercially available razor blade with regard to the cutting resistance in the case of cutting the single hair. As a result, it was confirmed that the razor blade of this Example is one-tenth smaller in the cutting resistance than the commercially available razor blade. In addition, three of the razor blades were arranged in parallel, and mounted on a required body by use of a dedicated jig. A shaving process was performed, while these razor blades being pressed against the skin. Since the size of the square opening is very small, smooth shaving was achieved without causing any injury of the skin.
EXAMPLE 3By cutting a (100) single crystal silicon block into a thin sheet, a Si wafer having the thickness of 0.3 mm was obtained. Then, square openings (blade openings) having the size of 1.5 mm×1.5 mm were formed in a pattern shown in
In addition, an electric shaver having the capability of providing microvibrations of this razor blade at an amplitude of approximately 0.2 mm and a frequency of vibration of 50 Hz was experimentally manufactured. Due to the microvibrations of the razor blade, it was possible to lead grown beards having relatively long lengths into the blade openings with reliability and efficiently cut the beards. As a safety device, a pressure sensor was mounted in one of the blade openings of the razor blade. In this case, it is possible to detect a pressure value at the time of pressing the razor blade against the skin. Therefore, when the razor blade was pressed against the skin at an excessive pressure, it was possible to give a caution to the user by an alarm sound.
As an additional experiment of this Example, a silicon oxide layer having the thickness of 10 nm was formed in a bottom surface 12 of the razor blade that contacts the skin in use. As a result of performing a shaving test, while allowing the bottom surface 12 of the razor blade to contact the skin, as shown in
A polycrystalline silicon block having a crystal grain size of approximately 10 mm was cut to obtain a sheet-like silicon single crystal having the thickness of 0.3 mm and the square shape of 7 mm×7 mm. Then, rectangular openings (blade openings) having the size of 1.5 mm×10 mm were formed in a pattern shown in
From a SEM observation of the cutting edge 10 of the obtained razor blade 1, it was confirmed that the nose radius (R) of the cutting edge is smaller than 10 nm. In this Example, since the cutting edge forming portions 14 and the cutting edge free portions 15 are arranged in the staggered manner along the longitudinal direction of the rectangular opening, injury of the skin was not caused by traveling the razor blade 1 in a direction parallel with the cutting edge, even when the size in the longitudinal direction of the opening increased.
EXAMPLE 5By cutting a (110) single crystal silicon block into a thin sheet, a Si wafer having the thickness of 0.3 mm was obtained. Then, square openings (blade openings) having the size of 0.6 mm×0.6 mm were formed in a pattern shown in
By cutting a (110) single crystal silicon block into a thin sheet, a Si wafer having the thickness of 0.3 mm was obtained. Then, square openings (blade openings) having the size of 1.5 mm×1.5 mm were formed in a pattern shown in
By cutting a (110) single crystal silicon block into a thin sheet, a Si wafer having the thickness of 0.3 mm was obtained. Then, square openings (blade openings) having the size of 1.5 mm×1.5 mm were formed in a pattern shown in
Selective oxidation was performed to a razor blade 1 manufactured according to the same method as Example 3. That is, as shown in
A vacuum deposition of gold (Au) was performed on a razor blade manufactured according to the same method as Example 3. That is, as shown in
An electron irradiation treatment was performed to a razor blade manufactured according to the same method as Example 3. That is, as shown in
An electron irradiation treatment was performed to a razor blade manufactured according to the same method as Example 3. That is, as shown in
As shown in
As shown in
As shown in
A polycrystalline silicon block composed of fine silicon crystal grains, by which a cutting edge made of silicon single crystal can not be obtained, was cut to a polycrystalline thin sheet having the thickness of 0.3 mm and the square shape of 7 mm×7 mm. Then, square openings having the size of 1.5 mm×1.5 mm were formed in the same pattern shown in
From a SEM observation of the cutting edge of the obtained razor blade, it was confirmed that the cutting edge is made of polycrystalline silicon, and recesses are formed at the grain boundary of the polycrystalline silicon by micro chipping. As a result, a sharp cutting edge was not obtained.
Example Comparative 2Square openings (blade openings) having the size of 1.5 mm×1.5 mm were formed in a stainless steel sheet having the thickness of 35 μm by machining. In addition, cutting edges having the cutting edge angle of 30° were formed so as to project in each of the openings. Subsequently, quenching was performed to the obtained razor blade to obtain the Vickers's hardness (Hv) of 650. A surface of this razor blade that contacts the skin in use was polished. From a SEM observation of the cutting edge, it was confirmed that a nose radius (R) of the cutting edge is approximately 1 μm. A shaving test was performed by use of this razor blade under a wet condition. As a result, good cutting performance was not obtained because of an insufficient cut of the cutting edge in the beard. In addition, an injury of the skin occurred during the shaving test.
INDUSTRIAL APPLICABILITYAccording to the present invention, at least one opening, and preferably a plurality of openings is formed in a silicon thin sheet of silicon single crystal or polycrystalline silicon including relatively large silicon crystal grains. Then, a cutting edge made of silicon single crystal is formed without depending on machining so as to project into the opening and have a nose radius is 0.5 μm or less, and preferably 0.1 μm or less. Therefore, the razor blade can provide an improved safety by preventing the occurrence of an accident such as an injury of the skin caused by mistake, and remarkably reduced cutting resistance for hair or beard, as compared with conventional razor blades.
Claims
1. A razor blade comprising:
- a silicon thin sheet having a plurality of openings and a cutting edge projecting into each of said openings,
- wherein said cutting edge is made of silicon single crystal, a nose radius of said cutting edge is 0.5 μm or less, each of said openings has a rectangular shape and is arranged in substantially parallel with an adjacent one of said openings, said cutting edge is provided at a longitudinal side of each of said openings and has cutting-edge forming portions and cutting-edge free portions, and said cutting-edge forming portions and said cutting-edge free portions of said cutting edge are arranged in a staggered manner in said longitudinal direction of said openings.
2. The razor blade as set forth in claim 1, wherein said silicon thin sheet is made of a silicon single crystal.
3. The razor blade as set forth in claim 1, wherein the nose radius of said cutting edge is 0.1 μm or less.
4. The razor blade as set forth in claim 1, wherein said razor blade is a net blade made of said silicon thin sheet and said cutting edge projecting into each of said openings.
5. The razor blade as set forth in claim 1, wherein said cutting edge extends in the longitudinal direction of each of said openings.
6. The razor blade as set forth in claim 1, wherein a cutting-edge angle, which is defined between a bottom surface of said razor blade and an inclined surface extending in said opening from a top surface of said razor blade to said bottom surface, is within a range of 10 degrees to 45 degrees.
7. The razor blade as set forth in claim 1, wherein said cutting edge is formed only at a single side of said opening.
8. The razor blade as set forth in claim 1, wherein said cutting edge is formed only at opposed two sides of said opening.
9. The razor blade as set forth in claim 1 wherein said cutting edge has an amorphous silicon layer thereon.
10. The razor blade as set forth in claim 1, comprising a polycrystalline silicon layer formed at a region other than a nose of said cutting edge.
11. The razor blade as set forth in claim 1, comprising microscopic asperities in a surface of the razor blade, to which a skin contacts in use.
12. The razor blade as set forth in claim 1, wherein a slot is formed in a bottom surface of the razor blade, to which a skin contacts in use, and has a shape of reducing contact resistance between the skin and the razor blade.
13. The razor blade as set forth in claim 1, wherein a slot is formed in a surface of the razor blade, to which a skin contacts in use, and has a shape of facilitating an introduction of an object to be cut into said opening.
14. The razor blade as set forth in claim 1, wherein the razor blade comprises a silicon oxide layer formed on a surface of the razor blade, to which a skin contacts in use.
15. The razor blade as set forth in claim 1, wherein said cutting edge has a silicon oxide layer thereon.
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Type: Grant
Filed: May 27, 2002
Date of Patent: Oct 24, 2006
Patent Publication Number: 20040143975
Assignee: Matsushita Electric Works, Ltd. (Kadoma)
Inventors: Tadashi Hamada (Sakai), Shinji Fujimoto (Neyagawa), Shigetoshi Sakon (Hirakata), Takashi Kozai (Inukami-gun)
Primary Examiner: Hwei-Siu Payer
Attorney: Oblon, Spivak, McClelland, Maier & Neustadt, P.C.
Application Number: 10/478,209
International Classification: B26B 21/58 (20060101); B26B 21/56 (20060101);